This invention relates to means for collimating a beam of radiation and converting the beam of radiation from a substantially elliptical cross sectional configuration into a beam of radiation of circular cross sectional configuration.
As is well documented in the art, the use of lasers, and now, in particular semiconductor lasers, play an important roll as the radiation or light sources for optical recording and reproducing systems. In such applications, it is desirable that the spot of radiation be circular and have a uniform intensity distribution. This is particularly true relative to semiconductor lasers, such as GaAs/GaAlAs heterostructure lasers, which, due to the p-n junction plane of radiation, causes the beam of emission to be elliptical, with the long axis of elliptical cross sectional configuration being parallel to the laser p-n junction.
Elaborate lens systems have been developed to meet the need of uniform intensity distribution and circular configuration. One example is disclosed in U.S. Pat. No. 4,333,173 wherein in combination with a coupling and objective lens system, a prism is employed whereby the beam collimation and conversion of an elliptically shaped beam into a circular beam is rendered possible.
The disadvantage of this system is the number of optical elements necessary to accomplish the desired results of collimation and conversion including the precision and costly manufacture of the prism relative to the type of semiconductor laser and its divergence angle of beam admission and the securence of these system components in fixed relation for a particular application.